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Abstract

In this work, the effects of thalassemia, a blood disease quite diffuse in the Mediterranean sea region, have been investigated at single cell level using a Raman Tweezers system. By resonant excitation of hemoglobin Raman bands, we have examined the oxygenation capability of β-thalassemic erythrocytes. A reduction of this fundamental erythrocyte function has been found. The measurements have been performed on a significant number of red blood cells; the relative statistical analysis is presented. Moreover, the response to photo-induced oxidative stress of diseased cells with respect to the normal ones has been analyzed. Finally, the deformability of thalassemic erythrocytes has been quantified by measuring the membrane shear modulus by using a double-trap system: the measurements have revealed an increase in membrane rigidity of more than 40%, giving evidence that the genetic defect associated to thalassemia, which manly relies on hemoglobin structure, also strongly affects the erythrocyte mechanical properties. Our results demonstrate that the developed set-up may have potential for the monitoring of blood diseases and their response to drug therapies.

Upper part: Typical Raman spectrum of an healthy RBC, obtained with an integration time of 10 s. The solid line corresponds to a fitting with 14 Lorentzian profiles, while the dashed lines indicate the deconvoluted curves. Lower part: Residual obtained as the difference between the experimental and the best-fit spectrum.

Comparison between the Raman spectra of normal and β-thalassemic RBC. The arrows indicate the spectral features affected by intensity changes, while the dashed lines highlight the observed energy shift.

A: Statistical distributions of the ratio R=Iν37/Iν11 obtained by analyzing 300 RBCs from a single normal (pink histogram) and thalassemic (blue histogram) donor. The fitting of these distributions with Gaussian profile is also shown. B: Gaussian profiles obtained by fitting the experimental distributions relative to 6 normal (Hi) and 6 thalassemic (Ti) volunteers. The weighted-mean and the standard deviation for the two kinds of cells are evidenced by horizontal bars.

Tables (2)

Table 1. Assignment and spectral position (cm-1) of the Hb Raman bands observed in this work. For comparison, we also report the bands observed by Wood et al. [32] for both oxyand deoxy-Hb with excitation at 514 nm.

Metrics

Table 1.

Assignment and spectral position (cm-1) of the Hb Raman bands observed in this work. For comparison, we also report the bands observed by Wood et al. [32] for both oxyand deoxy-Hb with excitation at 514 nm.

Table 2.

Tables (2)

Table 1.

Assignment and spectral position (cm-1) of the Hb Raman bands observed in this work. For comparison, we also report the bands observed by Wood et al. [32] for both oxyand deoxy-Hb with excitation at 514 nm.